Coal

Coal

Example chemical structure of coal

Coal is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. Coal is a readily combustible black or brownish-black rock. It is a sedimentary rock, but the harder forms, such as anthracite coal, can be regarded as metamorphic rocks because of later exposure to elevated temperature and pressure. It is composed primarily of carbon along with assorted other elements, including sulfur. It is the largest single source of fuel for the generation of electricity world-wide, as well as the largest world-wide source of carbon dioxide emissions, slightly ahead of petroleum and about double that of natural gas. Coal is extracted from the ground by coal mining, either underground mining or open pit mining (surface mining).

Types of coal

As geological processes apply pressure to dead matter over time, under suitable conditions, it is transformed successively into

• Peat, considered to be a precursor of coal. It has industrial importance as a fuel in some countries, for example, Ireland and Finland.
• Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
• Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation.
• Bituminous coal, a dense coal, usually black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
• Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating.
• Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used as pencil lead and, when powdered, as a lubricant.

The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:

Name	Volatiles %	C Carbon %	H Hydrogen %	O Oxygen %	S Sulfur %	Heat content kJ/kg
Braunkohle (Lignite)	45-65	60-75	6.0-5.8	34-17	0.5-3	<28470
Flammkohle (Flame coal)	40-45	75-82	6.0-5.8	>9.8	~1	<32870
Gasflammkohle (Gas flame coal)	35-40	82-85	5.8-5.6	9.8-7.3	~1	<33910
Gaskohle (Gas coal)	28-35	85-87.5	5.6-5.0	7.3-4.5	~1	<34960
Fettkohle (Fat coal)	19-28	87.5-89.5	5.0-4.5	4.5-3.2	~1	<35380
Esskohle (Forge coal)	14-19	89.5-90.5	4.5-4.0	3.2-2.8	~1	35380
Magerkohle (Non baking coal)	10-14	90.5-91.5	4.0-3.75	2.8-3.5	~1	<35380
Anthrazit (Anthracite)	7-12	>91.5	<3.75	<2.5	~1	<35300

The middle six grades in the table represent a progressive transition from the English-language sub-bituminous to bituminous coal, while the last class is an approximate equivalent to anthracite, but more inclusive (the U.S. anthracite has < 8% volatiles).

Early use

A 120,000-year-old Stone Age coalstone hunting camp was discovered in 2005 by archaelogists in an opencast coalstone mine in Germany, its first known use being campfire cooking fuel for German hunters. China Coal Information Institute reports the Chinese mined coalstone for fuel since 10,000 years ago at the time of the New Stone Age, or Neolithic Era. "People in Shanxi, now the largest coal production base, have been burning coal as fuel since then." Outcrop coal was used in Britain during the Bronze Age (2-3000 years BC), where it has been detected as forming part of the composition of funeral pyres. It was also commonly used in the early period of the Roman occupation: Evidence of trade in coal (dated to about AD 200) has been found at the inland port of Heronbridge, near Chester, and in the Fenlands of East Anglia, where coal from the Midlands was transported via the Car Dyke for use in drying grain. Coal cinders have been found in the hearths of villas and military forts, particularly in Northumberland, dated to around AD 400. In the west of England contemporary writers described the wonder of a permanent brazier of coal on the altar of Minerva at Aquae Sulis (modern day Bath) although in fact easily-accessible surface coal from what is now the Somerset coalfield was in common use in quite lowly dwellings locally.

However, there is no evidence that the product was of great importance in Britain before the High Middle Ages, after about AD 1000. Mineral coal came to be referred to as "seacoal," probably because it came to many places in eastern England, including London, by sea. This is accepted as the more likely explanation for the name than that it was found on beaches, having fallen from the exposed coal seams above or washed out of underwater coal seam outcrops. These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground mining from shafts or adits was developed. In London there is still a Seacoal Lane (off the north side of Ludgate Hill) where the coal merchants used to conduct their business. An alternative name was "pitcoal," because it came from mines. It was, however, the development of the Industrial Revolution that led to the large-scale use of coal, as the steam engine took over from the water wheel.

Uses today

File:DSCN4524 ashtabulacoalcars e2.jpg

Coal rail cars in Ashtabula, Ohio.

Coal as fuel

See also Clean coal technology and Fossil fuel power plant

Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption is about 6.2 billion tons annually, of which about 75% is used for the production of electricity. China produced 2.38 billion tonnes in 2006 and India produced about 447.3 million tonnes in 2006. 83.2% of China's electricity comes from coal. The USA consumes about 1.053 billion tonnes of coal each year, using 90% of it for generation of electricity. The world in total produced 6.19 billion tonnes of coal in 2006.

When coal is used for electricity generation, it is usually pulverized and then burned in a furnace with a boiler. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process has been improved over time. "Standard" steam turbines have topped out with some of the most advanced reaching about 35% thermodynamic efficiency for the entire process, which means 65% of the coal energy is rejected as waste heat into the surrounding environment. Old coal power plants, especially "grandfathered" plants, are significantly less efficient and reject higher levels of waste heat.

The emergence of the supercritical turbine concept envisions running a boiler at extremely high temperatures and pressures with projected efficiencies of 46%, with further theorized increases in temperature and pressure perhaps resulting in even higher efficiencies.

Other efficient ways to use coal are combined cycle power plants, combined heat and power cogeneration, and an MHD topping cycle.

Approximately 40% of the world electricity production uses coal. The total known deposits recoverable by current technologies, including highly polluting, low energy content types of coal (i.e., lignite, bituminous), might be sufficient for 300 years' use at current consumption levels, although maximal production could be reached within decades (see World Coal Reserves, below).

A more energy-efficient way of using coal for electricity production would be via solid-oxide fuel cells or molten-carbonate fuel cells (or any oxygen ion transport based fuel cells that do not discriminate between fuels, as long as they consume oxygen), which would be able to get 60%–85% combined efficiency (direct electricity + waste heat steam turbine). Currently these fuel cell technologies can only process gaseous fuels, and they are also sensitive to sulfur poisoning, issues which would first have to be worked out before large scale commercial success is possible with coal. As far as gaseous fuels go, one idea is pulverized coal in a gas carrier, such as nitrogen. Another option is coal gasification with water, which may lower fuel cell voltage by introducing oxygen to the fuel side of the electrolyte, but may also greatly simplify carbon sequestration.

Coking and use of coke

Main article: Coke (fuel)

Coke burning

Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F) so that the fixed carbon and residual ash are fused together. Metallurgic coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu/ton (29.6 MJ/kg). Byproducts of this conversion of coal to coke include coal tar, ammonia, light oils, and "coal gas".

Petroleum coke is the solid residue obtained in oil refining, which resembles coke but contains too many impurities to be useful in metallurgical applications.

Gasification

See also: Underground Coal Gasification

High prices of oil and natural gas are leading to increased interest in "BTU Conversion" technologies such as gasification, methanation and liquefaction.

Coal gasification breaks down the coal into its components, usually by subjecting it to high temperature and pressure, using steam and measured amounts of oxygen. This leads to the production of syngas, a mixture mainly consisting of carbon monoxide (CO) and hydrogen (H₂).

In the past, coal was converted to make coal gas, which was piped to customers to burn for illumination, heating, and cooking. At present, the safer natural gas is used instead. South Africa still uses gasification of coal for much of its petrochemical needs.

The Synthetic Fuels Corporation was a U.S. government-funded corporation established in 1980 to create a market for alternatives to imported fossil fuels (such as coal gasification). The corporation was discontinued in 1985.

Gasification is also a possibility for future energy use, as the produced syngas can be cleaned-up relatively easily leading to cleaner burning than burning coal directly (the conventional way). The cleanliness of the cleaned-up syngas is comparable to natural gas enabling to burn it in a more efficient gas turbine rather than in a boiler used to drive a steam turbine. Syngas produced by gasification can be CO-shifted meaning that the combustible CO in the syngas is transferred into carbon dioxide (CO₂) using water as a reactant. The CO-shift reaction also produces an amount of combustible hydrogen (H₂) equal to the amount of CO converted into CO₂. The CO₂ concentrations (or rather CO₂ partial pressures) obtained by using coal gasification followed by a CO-shift reaction are much higher than in case of direct combustion of coal in air (which is mostly nitrogen). These higher concentrations of carbon dioxide make carbon capture and storage much more economical than it otherwise would be.

Liquefaction - Coal-To-Liquids (CTL)

Coals can also be converted into liquid fuels like gasoline or diesel by several different processes. The Fischer-Tropsch process of indirect synthesis of liquid hydrocarbons was used in Nazi Germany for many years and is today used by Sasol in South Africa. Coal would be gasified to make syngas (a balanced purified mixture of CO and H₂ gas) and the syngas condensed using Fischer-Tropsch catalysts to make light hydrocarbons which are further processed into gasoline and diesel. Syngas can also be converted to methanol, which can be used as a fuel, fuel additive, or further processed into gasoline via the Mobil M-gas process.

A direct liquefaction process Bergius process (liquefaction by hydrogenation) is also available but has not been used outside Germany, where such processes were operated both during World War I and World War II. SASOL in South Africa has experimented with direct hydrogenation. Several other direct liquefaction processes have been developed, among these being the SRC-I and SRC-II (Solvent Refined Coal) processes developed by Gulf Oil and implemented as pilot plants in the United States in the 1960s and 1970s.

Another direct hydrogenation process was explored by the NUS Corporation in 1976 and patented by Wilburn C. Schroeder. The process involved dried, pulverized coal mixed with roughly 1wt% molybdenum catalysis. Hydrogenation occurred by use of high temperature and pressure synthesis gas produced in a separate gasifier. The process ultimately yielded a synthetic crude product, Naphtha, a limited amount of C₃/C₄ gas, light-medium weight liquids (C₅-C₁₀) suitable for use as fuels, small amounts of NH₃ and significant amounts of CO₂.

Yet another process to manufacture liquid hydrocarbons from coal is low temperature carbonization (LTC). Coal is coked at temperatures between 450 and 700°C compared to 800 to 1000°C for metallurgical coke. These temperatures optimize the production of coal tars richer in lighter hydrocarbons than normal coal tar. The coal tar is then further processed into fuels. The Karrick process was developed by Lewis C. Karrick, an oil shale technologist at the U.S. Bureau of Mines in the 1920s.

All of these liquid fuel production methods release carbon dioxide (CO₂) in the conversion process, far more than is released in the extraction and refinement of liquid fuel production from petroleum. If these methods were adopted to replace declining petroleum supplies, carbon dioxide emissions would be greatly increased on a global scale. For future liquefaction projects, Carbon dioxide sequestration is proposed to avoid releasing it into the atmosphere, though no pilot projects have confirmed the feasibility of this approach on a wide scale. As CO₂ is one of the process streams, sequestration is easier than from flue gases produced in combustion of coal with air, where CO₂ is diluted by nitrogen and other gases. Sequestration will, however, add to the cost.

Coal liquefaction is one of the backstop technologies that could potentially limit escalation of oil prices and mitigate the effects of transportation energy shortage that some authors have suggested could occur under peak oil. This is contingent on liquefaction production capacity becoming large enough to satiate the very large and growing demand for petroleum. Estimates of the cost of producing liquid fuels from coal suggest that domestic U.S. production of fuel from coal becomes cost-competitive with oil priced at around 35 USD per barrel, (break-even cost). This price, while above historical averages, is well below current oil prices. This makes coal a viable financial alternative to oil for the time being, although production is not great enough to make synfuels viable on a large scale.

Among commercially mature technologies, advantage for indirect coal liquefaction over direct coal liquefaction are reported by Williams and Larson (2003). Estimates are reported for sites in China where break-even cost for coal liquefaction may be in the range between 25 to 35 USD/barrel of oil.'

Intensive research and project developments have been implemented from 2001. The World CTL Award is granted to personalities having brought eminent contribution to the understanding and development of Coal liquefaction.

Coal as a traded commodity

The price of coal has gone up from around $30 a tonne in 2000 to around $130 a tonne in 2008.

In North America, a Central Appalachian coal futures contract is currently traded on the New York Mercantile Exchange (trading symbol QL). The trading unit is 1,550 tons per contract, and is quoted in U.S. dollars and cents per ton. Since coal is the principal fuel for generating electricity in the United States, the futures contract provides coal producers and the electric power industry an important tool for hedging and risk management.

In addition to the NYMEX contract, the IntercontinentalExchange (ICE) has European (Rotterdam) and South African (Richards Bay) coal futures available for trading. The trading unit for these contracts is 5,000 tons, and are also quoted in U.S. dollars and cents per ton.

Cultural usage

Coal is the official state mineral of Kentucky and the official state rock of Utah. Both U.S. states have a historic link to coal mining.

Some cultures uphold that children who misbehave will receive coal from Santa Claus for Christmas in their stockings instead of presents.

It is also customary and lucky in Scotland to give coal as a gift on New Year's Day. It happen's as part of First-Footing and represents warmth for the year to come.

Environmental effects

Coal mining

Coal mining causes a number of harmful effects. When coal surfaces are exposed, pyrite (iron sulfide), also known as "fool's gold", comes in contact with water and air and forms sulfuric acid. As water drains from the mine, the acid moves into the waterways, and as long as rain falls on the mine tailings the sulfuric acid production continues, whether the mine is still operating or not. This process is known as acid rock drainage (ARD) or acid mine drainage (AMD). If the coal is strip mined, the entire exposed seam leaches sulfuric acid, leaving the subsoil infertile on the surface and begins to pollute streams by acidifying and killing fish, plants, and aquatic animals who are sensitive to drastic pH shifts.

By the late 1930s, it was estimated that American coal mines produced about 2.3 million tons of sulfuric acid annually. In the Ohio River Basin, where twelve hundred operating coal mines drained an estimated annual 1.4 million tonnes of sulfuric acid into the waters in the 1960s and thousands of abandoned coal mines leached acid as well. In Pennsylvania alone, mine drainage had blighted 2,000 stream miles by 1967.

Coal burning

Combustion of coal, like any other fossil fuel, occurs due to an exothermic reaction between the components of the fuel source, and the components air surrounding it. Coal is made primarily of carbon, but also contains sulfur, oxygen and hydrogen. The reaction between coal and the air surrounding it produces oxides of carbon, usually carbon dioxide (CO₂) in a complete combustion, along with oxides of sulfur, mainly sulfur dioxide (SO₂), and various oxides of nitrogen (NO_x). Because of the hydrogen and nitrogen components of air, hydrides and nitrides, of carbon and sulfur, are also produced during the combustion of coal in air. These could include hydrogen cyanide (HCN), sulfur nitrate (SNO₃) and many other toxic substances.

Further, acid rain may occur when the sulfur dioxide produced in the combustion of coal, reacts with oxygen to form sulfur trioxide (SO₃), which then reacts with water molecules in the atmosphere to form sulfuric acid (see Acid anhydride for more information). The sulfuric acid (H₂SO₄) is returned to the Earth as acid rain. Flue gas desulfurization scrubbing systems, which use lime to remove the sulfur dioxide can reduce or eliminate the likelihood of acid rain.

However, another form of acid rain is due to the carbon dioxide emissions of a coal plant. When released into the atmosphere, the carbon dioxide molecules react with water molecules, to produce carbonic acid (H₂CO₃). This, in turn, returns to the earth as a corrosive substance. This cannot be prevented as easily as sulfur dioxide emissions can, because carbon is the main component of coal, and this resultantly means that a person cannot as easily reduce carbon dioxide emissions caused in the oxidation of coal, as they can with the afforementioned use of lime to reduce sulfur dioxide emissions.

Emissions from coal-fired power plants represents one of the two largest sources of carbon dioxide emissions, believed to be the cause of global warming. Coal mining and abandoned mines also emit methane, another purported cause of global warming. Since the carbon content of coal is higher than oil, burning coal is a serious threat to the stability of the global climate, as this carbon forms CO₂ when burned. Many other pollutants are present in coal power station emissions, as solid coal is more difficult to clean than oil, which is refined before use. A study commissioned by environmental groups claims that coal power plant emissions are responsible for tens of thousands of premature deaths annually in the United States alone. Modern power plants utilize a variety of techniques to limit the harmfulness of their waste products and improve the efficiency of burning, though these techniques are not subject to standard testing or regulation in the U.S. and are not widely implemented in some countries, as they add to the capital cost of the power plant. To eliminate CO₂ emissions from coal plants, carbon capture and storage has been proposed but has yet to be commercially used.

Coal and coal waste products including fly ash, bottom ash, and boiler slag, contain many heavy metals, including arsenic, lead, mercury, nickel, sulphur, vanadium, beryllium, cadmium, barium, chromium, copper, molybdenum, zinc, selenium and radium, which are dangerous if released into the environment. Coal also contains low levels of uranium, thorium, and other naturally-occurring radioactive isotopes whose release into the environment may lead to radioactive contamination. While these substances are trace impurities, enough coal is burned that significant amounts of these substances are released, resulting in more radioactive waste than nuclear power plants. Mercury emissions from coal burning are concentrated as they work their way up the food chain and converted into methylmercury, a toxic compound that may affect people who frequently consume freshwater fish caught near some coal-fired power plants. There is however likely to be little relationship between power plant emissions and methylmercury levels in ocean fish.

Energy density

Main article: Energy value of coal

The energy density of coal, i.e. its heating value, is roughly 24 megajoules per kilogram.

The energy density of coal can also be expressed in kilowatt-hours, the units that electricity is most commonly sold in, to estimate how much coal is required to power electrical appliances. The energy density of coal is 6.67 kWh/kg and the typical thermodynamic efficiency of coal power plants is about 30%. Of the 6.67 kWh of energy per kilogram of coal, about 30% of that can successfully be turned into electricity - the rest is waste heat. Coal power plants obtain approximately 2.0 kWh per kg of burned coal.

As an example, running one 100 watt computer for one year requires 876 kWh (100 W × 24 h × 365 {days in a year} = 876000 Wh = 876 kWh). Converting this power usage into physical coal consumption: ${\frac {876\ \mathrm {kW\cdot hours} }{2.0\ \mathrm {kW\cdot hours/kg} }}=438\ \mathrm {kg\ of\ coal} =967\ \mathrm {pounds\ of\ coal}$

It takes 438 kg (967 pounds) of coal to power a computer for one full year. One should also take into account transmission and distribution losses caused by resistance and heating in the power lines, which is in the order of 5 - 10%, depending on distance from the power station and other factors.

Relative carbon cost

Because coal is at least 50% carbon (by mass), then 1 kg of coal contains at least 0.5 kg of carbon, which is ${\frac {0.5\mathrm {kg} }{\mathrm {12} \cdot \mathrm {kg/kmol} }}={\frac {1}{24}}\mathrm {kmol}$ where 1 mol is equal to N_A (Avogadro Number) particles. This combines with oxygen in the atmosphere during combustion, producing carbon dioxide, with an atomic weight of (12 + 16 × 2 = mass(CO₂) = 44 kg/kmol). ${\frac {1}{24}}\mathrm {kmol}$ of CO₂ is produced from the ${\frac {1}{24}}\mathrm {kmol}$ present in every kilogram of coal, which once trapped in CO₂ weighs approximately ${\frac {1}{24}}\mathrm {kmol} \cdot {\frac {44\mathrm {kg} }{\mathrm {kmol} }}={\frac {11}{6}}\mathrm {kg} \approx 1.83\mathrm {kg}$.

This can be used to put a carbon-cost of energy on the use of coal power. Since the useful energy output of coal is about 30% of the 6.67 kWh/kg(coal), we can say about 2 kWh/kg(coal) of energy is produced. Since 1 kg coal roughly translates as 1.83 kg of CO₂, we can say that using electricity from coal produces CO₂ at a rate of about 0.915 kg CO₂/kWh, or about 0.254 kg CO₂/MJ.

This estimate compares favourably with the U.S. Energy Information Agency's 1999 report on CO₂ emissions for energy generation, which quotes a specific emission rate of 950 g CO₂/kWh. By comparison, generation from oil in the U.S. was 890 g CO₂/kWh, while natural gas was 600 g CO₂/kWh. Estimates for specific emission from nuclear power, hydro, and wind energy vary, but are about 100 times lower. See indirect carbon emissions from nuclear power for estimates.

Coal fires

There are hundreds of coal fires burning around the world. Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface wildfires. Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. A grass fire in a coal area can set dozens of coal seams on fire. Coal fires in China burn 109 million tonnes of coal a year, emitting 200 million tonnes of carbon dioxide. This amounts to 2-3% of the annual worldwide production of CO₂ from fossil fuels, or as much as emitted from all of the cars and light trucks in the United States. In Centralia, Pennsylvania (a borough located in the Coal Region of the United States) an exposed vein of coal ignited in 1962 due to a trash fire in the borough landfill, located in an abandoned anthracite strip mine pit. Attempts to extinguish the fire were unsuccessful, and it continues to burn underground to this day. The Australian Burning Mountain was originally believed to be a volcano, but the smoke and ash comes from a coal fire which may have been burning for over 5,500 years.

At Kuh i Malik in Yagnob Valley, Tajikistan, coal deposits have been burning for thousands of years, creating vast underground labyrinths full of unique minerals, some of them very beautiful. Local people once used this method to mine ammoniac. This place has been well-known since the time of Herodotus, but European geographers mis-interpreted the Ancient Greek descriptions as the evidence of active volcanism in Turkestan (up to the 19th century, when Russian army invaded the area).

The reddish siltstone rock that caps many ridges and buttes in the Powder River Basin (Wyoming), and in western North Dakota is called porcelanite, which also may resemble the coal burning waste "clinker" or volcanic "scoria". Clinker is rock that has been fused by the natural burning of coal. In the Powder River Basin approximately 27 to 54 billion tonnes of coal burned within the past three million years. Wild coal fires in the area were reported by the Lewis and Clark Expedition as well as explorers and settlers in the area.

Production trends

File:2005coal.PNG

Coal output in 2005

In 2006, China was the top producer of coal with 38% share followed by the USA and India, reports the British Geological Survey.

World coal reserves

At the end of 2006 the recoverable coal reserves amounted around 800 or 900 gigatonnes. The United States Energy Information Administration gives world reserves as 998 000 short tons (equal to 905 gigatonnes), approximately half of it being hard coal. At the current production rate, this would last 164 years. At the current global total energy consumption of 15 terawatt, there is enough coal to provide the entire planet with all of its energy for 57 years.

British Petroleum, in its annual report 2007, estimated at 2006 end, there were 909,064 million tons of proven coal reserves worldwide, or 147 years reserves to production ratio. This figure only includes reserves classified as "proven"; exploration drilling programs by mining companies, particularly in under-explored areas, are continually providing new reserves. In many cases, companies are aware of coal deposits that have not been sufficiently drilled to qualify as "proven". However, some nations haven't updated their information and assume reserves remain at the same levels even with withdrawals.

US coal regions

The United States Department of Energy uses estimates of coal reserves in the region of 1,081,279 million short tons (9.81 × 10¹⁴ kg), which is about 4,786 BBOE (billion barrels of oil equivalent). The amount of coal burned during 2001 was calculated as 2.337 GTOE (gigatonnes of oil equivalent), which is about 46 million barrels of oil equivalent per day. Were consumption to continue at that rate those reserves would last about 285 years. As a comparison, natural gas provided 51 million barrels (oil equivalent), and oil 76 million barrels, per day during 2001.

However, according to New Scientist, reported reserves of some countries have fallen quite a lot in recent years, and there is much doubt about the reserves reported by other countries. Using Hubbert peak theory, it seems that the total amount of coal that will ever be mined will attain only about 450 gigatonnes. This is much less than what is assumed in calculations of global warming, and it implies that other sources of energy need to be developed.

Of the three fossil fuels coal has the most widely distributed reserves; coal is mined in over 100 countries, and on all continents except Antarctica. The largest reserves are found in the USA, Russia, Australia, China, India and South Africa.

Note the table below.

Proved recoverable coal reserves at end-2006 (million tonnes (Teragrams))

Country	Bituminous (including anthracite)	Sub- bituminous and lignite	TOTAL	Share
United States of America	111,338	135,305	246,643	27.1
Russia	49,088	107,922	157,010	17.3
China	62,200	52,300	114,500	12.6
India	90,085	2,360	92,445	10.2
Australia	38,600	39,900	78,500	8.6
South Africa	48,750	-	48,750	5.4
Ukraine	16,274	17,879	34,153	3.8
Kazakhstan	28,151	3,128	31,279	3.4
Poland	14,000	-	14,000	1.5
Brazil	-	10,113	10,113	1.1
Germany	183	6,556	6,739	0.7
Colombia	6,230	381	6,611	0.7
Canada	3,471	3,107	6,578	0.7
Czech Republic	2,094	3,458	5,552	0.6
Indonesia	740	4,228	4,968	0.5
Turkey	278	3,908	4,186	0.5
Greece	-	3,900	3,900	0.4
Hungary	198	3,159	3,357	0.4
Pakistan	-	3,050	3,050	0.3
Bulgaria	4	2,183	2.187	0.2
Thailand	-	1,354	1,354	0.1
North Korea	300	300	600	0.1
New Zealand	33	538	571	0.1
Spain	200	330	530	0.1
Zimbabwe	502	-	502	0.1
Romania	22	472	494	0.1
Venezuela	479	-	479	0.1
TOTAL	478,771	430,293	909,064	100.0

Major coal exporters

Exports of Coal by Country and year (million tonnes)

Country	2003	2004
Australia	238.1	247.6
United States	43.0	48.0
South Africa	78.7	74.9
Former Soviet Union	41.0	55.7
Poland	16.4	16.3
Canada	27.7	28.8
China	103.4	95.5
South America	57.8	65.9
Indonesia	107.8	131.4
Total	713.9	764.0

See also

• Abiogenic petroleum origin
• Americans for Balanced Energy Choices (ABEC)
• Asphaltene
• Australian Coal Alliance
• Carbochemistry
• Carbon sequestration
• Charcoal
• Clean coal
• Coal assay
• Coal dust
• Coal in China
• Coal Measure (stratigraphic unit)
• Coal Mine Safety and Health Act of 1969 (in the US)
• Coal mining
• Coal mining debate
• Coal phase out
• Coal-tar
• Energy development
• Energy value of coal
• Fluidized bed combustion
• FutureGen
• Gasification
• Granular material
• History of coal mining
• List of environment topics
• Major coal producing regions
• Mountaintop removal mining
• Udston mining disaster
• Underground Coal Gasification
• World Coal Institute
• World energy resources and consumption

References

• The Face of Decline: The Pennsylvania Anthracite Region in the Twentieth Century. Cornell University Press. 2005. ISBN 0-8014-8473-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Rottenberg, Dan (2003). In the Kingdom of Coal; An American Family and the Rock That Changed the World. Routledge. ISBN 0-415-93522-9.
• Robert H. Williams and Eric D. Larson (December 2003). "A comparison of direct and indirect liquefaction technologies for making fluid fuels from coal" (PDF). Energy for Sustainable Development. VII: 103–129.
• Outwater, Alice (1996). Water: A Natural History. New York, NY: Basic Books. ISBN 0-465-03780-1.
• Smith, Duane A. (1993). Mining America: The Industry and the Environment, 1800-1980. Lawrence, KS: University Press of Kansas. p. 210. ISBN 0870813064. {{cite book}}: Unknown parameter |month= ignored (help)

External links

• http://www.euracoal.org European Association for Coal and Lignite
• http://www.coalonline.org/site/coalonline/content/home
• World Coal Institute
• Coal: Facts & Figures
• MSNBC report on coal pollution health effects in the United States
• Clean coal technologies
  • Advanced methods of using coal (Japanese Coal Energy Center)
• USDOE Hydrogen from Coal Research
• Coal Preparation, Journal of
• Wyoming Coal from the University of Wyoming
• Coal - origin, purification and consumption
• History of coal seams and the practice of coal mining in North Staffordshire, UK
• Energy Options: Coal a Nightly Business Report special
• World Coal-To-Liquids 2008 Conference 3 & 4 April, 2008 - Paris